A furnace may be equipped with regenerative burners that fire into a process chamber containing a load to be heated. The burners are ordinarily operated in firing cycles in which they discharge fuel and combustion air into the process chamber, alternating with nonfiring exhaust cycles in which hot gas from the process chamber is drawn outward through regenerative beds at the burners. This heats the regenerative beds which, in turn, heat streams of incoming combustion air that are driven through the regenerative beds in the firing cycles. The alternating regenerative firing and exhaust cycles provide the process chamber with hot air and fuel to produce an atmosphere of gaseous products of combustion for heating the load.